In PoE, limited power is transmitted to Ethernet-connected equipment (e.g., VoIP telephones, WLAN transmitters, security cameras, etc.) from an Ethernet switch. In a PoE system, DC power from the switch is transmitted over one or more twisted wire pairs. The same twisted wire pair may also transmit/receive differential data signals. In this way, the need for providing any external power source for the PDs can be eliminated. The standards for PoE and PoDL are set out in IEEE 802.3 and are well-known. The PSE's typically include one or more ICs that are specifically designed for a particular PoE configuration and cabling. There are a variety of cabling permutations, such as straight-thru, crossover, and Y-cables.
PSEs are sometimes given the option of which twisted wire pairs to power: the data pair and/or the spare pair. Certain high power PoE systems exceed the present IEEE limit of 25.5 W and must send power to the PD(s) over all four pairs simultaneously to share the power load.
What is needed is a single PSE design capable of detecting all types of PoE topologies using a single PSE architecture such that the PSE can support a variety of current and future PoE cabling and power permutations.